The invention relates to a gas burner comprising a burner gas, an air chamber around the gun and a combustion chamber, which air chamber debouches into the combustion chamber via an annular combustion mouth, the burner gun having a cylindrical barrel for the supply of gaseous fuel to the combustion chamber through the said combustion mouth and the annular combustion mouth having a convergent and divergent inner wall located on either side of a restriction situated outside the front end of the barrel of the burner gun.
In gas burners as defined, the gaseous fuel usually leaves the barrel via a slit provided therein, which slit is directed radially, i.e. outward, the barrel is usually double-walled, so that an ignition pilot burner may optionally be provided within the barrel.
A gas burner of this type may, for example, be used for the partial combustion of a gaseous fuel, in which the combustion gas obtained contains inter alia hydrogen and carbon monoxide. Such gases can be used, for example, for the synthesis of methanol or ammonia, for the reduction of sulphur compounds, or for treating petroleum fractions.
For the above application the burner is usually installed on a reactor lined with fire bricks, in which reactor the combustion gases have a certain residence time - which contributes to a fuller conversion of the fuel and diminishes the possibility of soot formation. The combustion chamber of the gas burner directly communicates with the reactor and serves to extend the residence time of gas and oxygen. The good mixing of these two latter components in the combustion chamber of the gas burner contributes to a suppression of the soot formation and renders operation at a low oxygen/fuel ratio possible, so that the hydrogen and carbon monoxide percentage in the combustion gas is high and the water and carbon dioxide percentage therein low.
It has already been proposed to improve the operation of the burner by blowing oxygen or an oxygen-containing gas such as air, tangentially into the air chamber, so that oxygen or air on its way to the combustion mouth moves in a helix round the barrel of the burner gun. The helical movement continues in the combustion chamber and contributes to a good mixing of oxygen and gaseous fuel.
By the combined use of the combustion chamber with the design of the burner gun as mentioned above, not only the above-mentioned helical vortex in the combustion chamber but also a loop-shaped recirculation of the reacting gases and their combustion products from the flame to the combustion mouth is obtained, which increases the residence time and consequently suppresses soot formation. Especially the shape of the combustion mouth and the location of the barrel of the burner with respect to the restruction of the combustion mouth contribute to the occurrence of this loop-shaped recirculation. As a result of the shape of the combustion mouth air or oxygen and the gaseous fuel flow into the combustion chamber in a fan-shaped pattern.